<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>

</body>
<script>
  function User () {

  }

  // console.dir()可以显示一个对象所有的属性和方法。
  console.dir(User)

</script>
</html>
